Rheostat



Lemma 2 Sheets-Sheet 1 RHEOS TAT lllllllll Filed oct. 25, 192e N. C. SCHELLENGER Sept. 15, 1931 SePt- 15, 1931. N. c, SCHELLENGER 1,823,473

RHEOSTAT Filed Oct. 25, 1926 2 Sheets-Shea?. 2

mwunum v Si IIIIIIIIIIIIIIIYIIIIII/ll Patented Sept. 115, 1931 UNITED STATES PATENT OFFICE NEWTON C. SOHELLENGER, OFVELKHART, INDIANA, ASSIGNOP. TO CHICAGO TELEPHONE SUPPLY COMPANY, vOF ELKHART, INDIANA, A CORPORATION OF DELAWARE RHEosTA'r Application lerl October 25, 1926. Serial No. 143,905.

In general the present invention pertains to electrical current control apparatus and more particularly to rheostats and potentiometers of the .same general character as that disclosed in my copending patent application,

Serial No. 114,126 filed June 7th, 1926.

In my aforesaid copending patent application, I disclose a highly simple and inexpensive rheostat wherein a few turns of the .1 resistance wire on the resistance strip were tact arm of the device to be moved freely to and from its-in and off position. This obviated the necessity of the arm having to move over or to strike a hump or raised portion. However, 1n order to accomplish the desired result, it was necessary, as disclosed in my copending application, to provide the strip with a notch. Obviously, this necessitated an additional operation in the manufacture of the strip.

I propose in accordance with the features of thefpresent invention, to provide a strip wherein the last few windings at each end are buried sufficiently deep in the edge of the core so as to be Aflush with the adjacent edge of the insulator strip without the necessity of previously notching thestrip. I accomplish this result by forcing the last few windings down into the edge of the strip by applying pressure to the resistance strip after the same has been wound. Also, the windings on the side of the strip are forced into the strip at each end for the purpose o f preventing `the windings from becoming unwound.

In accordance with other features of my invention'I provide a current control device such as a rheostat having a metallic frameI equipped with a plurality of vents serving as a means of circulation. These vents or apertures permit a continuous change of air to take place inside of the rheostats frame the metallicframe of the rheostat. The insulation employed preferably comprises a strip'of sheet -insulation adapted to be bent into an arcuate shape and an annular ring insulator. The insulating` strip is dis osed about the periphery of the metallic rame whereas the ring-like insulator is dis osed over a flange formed integral with the rame and serves to insulate one edge of the resistance strip from the flange.

Furthermore, in order to enhance the appearancemof the device of my invention I propose to provide means for enabling the resistance strip to maintain its generally circular form throughout itsflength. I accomplish this feature by placing a small washer under each end of the resistance strip where the wire has been omitted.

I desire itunderstood that although my inj vention is particularly u seful in'connection with rheostats and potentiometers, the invention is not to be thus limited since it can be used successfully in many other applications.

Other objects and advantages of my invention will more fully appear from the following detailed description taken in connection with the accompanying drawings which illustrate several embodiments thereof and in which Fig. 1 is an elevation showing my novel device applied to a mounting panel;

Fig. 2 is an enlarged sectional view taken on substantially the line 2--2 of Fig. 1 looking in a direction indicated by the arrows;

Fi 3 is a sectional view taken on substantlally the line 3-3'of Fig. 2 looking in the direction indicated by the arrows;

Fig. 4 is a perspective view of the insulator strip employed in my device;

Fig. 5 is a view of the ring-like insulating was/her used in conjunction with the insulator shown in Fig. 4;

Fig. 6 is a fragmentary view of an end of the resistance strip employed in my device illustrating the manner in whichV the end of the wire is embedded in the core of the strip;

Fig. 7 is a sectional view taken on the line 7-7 of Fig. 6; T

Fig. 8 is a sectional view taken on the line 8 8 of Fig. 6;

Fig. 9 is a fragemntary enlarged view of an end of my novel resistance strip showing the manner in which the last few windings are pressed into the edge of the strip to make them flush with the adjoining bared edge;

Fig. is an elevation similar to that shown in ig. 1 of a modification of my invention; an

Fig. 1l is a sectional view taken on the line 11-11 of Fig. 10 looking in the direction indicated by the arrows.

, Referring now to the drawings in detail in which like reference numerals designate similar parts throughout the several views, denotes generally a metallic frame of a current controller of preferably the rheostat type. I preferably make this frame of a circular form and provide it with an annular liange 21 which extends laterally therefrom and at right angles to the wall of the body. The frame is cuplike in shape and has one end Closed by a concave portion 22 formed integral therewith. It will be evident from Figure 2 that the concave portion is positioned within' the annular wall of the body and located at an end of the body opposite to that of the annular flange 21.

The concave or depressed portion 22 is equipped with an annular openin 23 disposed subst-antially centrally of the ody and preferably concentric with the body. Extending outwardly from the concave portion 22 are a pair .of prongs 24 and 25 which constitute stops and which are preferably punched from the portion 22 leaving aperflirres 26)and 27 respectively in the portion 22 ig. 1 I

A. tubular element or sleeve 28 is associated with the body and is disposed within the dimensions of the body. This sleeve has a reduced end 29 which extends through the opening 23 in the concave ortion 22. Itv will be evident from Fig. 2 t at the reduced portion 29 is firmly secured to the concave portion 22 by means of the turned-back portion 30 which may be formed by any conventional riveting apparatus or the like. In other words, the end of the reduced ortion 29 of the sleeve 28 is in reality sprea out over the surface of the concave portlon 22 to clench the sleeve thereto. In order to insure a tight connection between the concave ortion 22 and the riveted portion 30 I provi e the concave portion 22 with a substantially flat portion 31 which serves as a seat for the contact mechanism to be hereinafter described.

Sleeve 28 has a threaded core 32 into which is threaded a tubular sleeve or thimble 33. That is to say, the thimble 33 enters into a telescopic relationship with the sleeve 28.

.Also sleeve 33 has an enlarged head 34 between which end and the end of the 'sleeve 28 is a mounting panel 35.

Positioned between the panel and the annular flange 21 is a disc of insulating material 35 which insulates the ange from the panel. This insulator 35' enables a metallic panel to be used if it is so desired. The head 34 of the thimble 33 is preferably polygonal and abuts a metallic washer 34. Located between this metallic washer 34 and the anel 35 is a, fiber washer 33. Referring to ig. 2 it will be evident that the thimble 33 serves to firmly clamp the sleeve 28 to the panel 35 which results in the peripheral edge or fiange 21 of the body 20 being brought into relatively tight engagement with the insulating member 35. 1

Extending through the telescoping sleeves 28 and 33 is an operatingv shaft 36. Secured to the external end of the shaft 36 is a handle or knob 37 by means of which the shaft may be actuated. The shaft 36fis journaled in the bore 37 of sleeve 33 and in the reduced bore 38 of the reduced portion 29 of sleeve 28. The shaft 36 is provided with a reduced end .39 and a shoulder 40 which abuts the reduced portion 29 of sleeve 28.

Mounted upon the reduced end 39 of the shaft 36 is a resilient washer 41 the edge of which is castellated as indicated at 42. This washer is arcuate in shape and has an edge which engages the fiat portion 31 associated with the concave end 22 of the body 20. The purposes of this washer will be more fully explained hereinafter.

Also mounted upon the reduced portion 39 is a contact arm assembly which includes a contactarm 46 having an arcuate shaped mounting portion 47. The base or mounting portion 47 is provided with an arcuate slot 48 as well as with an offset portion 49 which is adapted to be flexed into and out of the plane of the mounting or base 47 as will become more apparent hereinafter. The contact arm 46 and its base 47 may be made of any suitable material such, for example, as nickel-silver or the like. Now the contact arm 46 includes a slanting portion 50 as well as an arcuate shaped contact portion 5l. I preferably provide the contact portion 50 with a curved shape so as to permit of a smooth movement when it passes over the resistance as will be described hereinafter. Located on the offset portion 49 is a collar or hub 52 having a bore 53 adapted to receive vt-he end 39 of the shaft 36. Collar 52 has formed integral therewith a reduced portion 54 which extends through an opening 55 in the offset portion 49 andis clenched to the offset portion 49 as shown in Fig. 2.

When the assembly 45 is removed from the end 39 of the shaft 36, the hub 52 and the portion 49 will assume a position lying in a plane at an angle to the plane of the portion 47 due to the resiliency of the portion 49 defined by the arcuate shaped slot48. However, when the assembly is mounted upon the shaft the portion 49 will be flexed into the same plane as the rest of the mounting or base 47 of the contact arm. This will result in the contact f portion 50 of the arm 46 being resiliently urged into engagement with the resistance wire or winding designated generally by the reference character 60. The collar 52 is provided with a set screw 61 by means of which the same may be fastened to the end 39 of the shaft.

Now the assembly 45 when in position on the shaft 36 is mounted contiguous with the resilient washer 41. This washer 41 not only serves as a resilient mounting for the assembly but also serves as a universal mounting due to its arcuate shape. This arrangement insures a smooth movement on the part of the contact arm throughout its range of movement. Moreover, it should be noted that with the exception ofthe contact portion 50 the entire Contact arm assembly 45 is disposed in the recess defined by the depressed portion 22 and within the dimensions of body 20 thus resulting in a very compact piece of electrical apparatus.

The resistance windings 60 previously referred to, are wound upon an insulator or core 62 in accordance with the winding process disclosed in the co-pending patent application of Charles I-Iavlish, Serial No. 729,479 filed August 1, 1924. The primary difference between the strip 62 that I employ and that disclosed in thefcopending patent application lies in the fact that Iprovide one .end of the strip with windings that are forced or pressed into the core 62. In practice the strip is wound from one end to the other and thereafter I 'preferably sever the last few windings on the end of the strip leaving the ends of the strip bare of wire windings. As shown in Figs. 6, 7 and 8 the last few turns at each end of the strip are pressed or forced into the adjoining portion of the core 62.

. Any suitable mechanism may be employed for causing the last few turns to be embedded at 63 in the core. By thus embedding the last fewturns at each end of the strip in the core the tendency of the windings of the strips to become unwound is vobviated to very great extent.` Also, it should be notedthat each end of the strip, or core 62 is provided with an aperture 63 for'enabling the strip to befastened to the body as shall appear hereinafter.

Referring now, to Fig. 9 I shall describe the embedding of the last few turns of the wires 60 on the strip in the edge of the strip. As shown at 64 the last two or three turns of each end of the strip are forced or pressed into the edge of the stripuntil the lastl turn is perfectly flush with the bared edge of the core. I have designated the adjoining edge of the core 62 by the reference character 65A. This bared portion 65 in reality constitutes an off-position for the contact arm 46. Obviously, the contact4 arm can be with facility, moved from the off-portion 65 onto vthe winding without having to strike an objecj.

tionable hump as has been the case heretofore.

After the strip has been Wound, it is bent into an arcuate shape and is disposed about the periphery of the body 20. Positioned j.' between the wound strip 62 and the periphery tioned on the flange 21 and abutting the 1 I adjacent edge of the windings 60 on the core .62 is an annular or ringlike insulating member 71 which serves lto insulate one edge of the resistance strip from the fiange 21. The two strips 62 and 70 are tightly drawn around the periphery of the body 20 and are secured at opposite ends to the body adjacent the prongs or stops 24 and 25 as will now be described in detail.

Referring to Fig. 3 it will be seen that each end of the resistance strip and the associa-ted end of the strip is secured to the wall of the body 20 adjacent one of the two prongs mentioned previously. One end of the wound core or strip 62 is secured to the frame 20 by means of a bolt 75. Also at this time it should be noted that the resistance strip is protected by a protective insulating strip 72 which encircles the resistance strip as is obvious from the drawings. The opposite ends of this protective strip are secured to the frame by the same bolts as -those which secure the other two strips to the frame. Bolt 75 extends through the apertures in the strips 62 and 70 as well as through the aperture73 in Now, in order to prevent the end of the ing distorted and so as to enable the strip to maintain its generally circular form, Irplace an insulating washer 78 beneath the end of the strip 62 and immediately overthe associated portion of the strip 70. The bolt 75 cooperates with the loclinuts 79 and l80 to firmly clamp the associated ends of the Varlous strips to the frame..

The other ends of the strips are fastened to the frame in much the same manner as the ends just described by the means of a bolt having awasher 76 and an insulating Washer 77 disposed about its "shank and locknuts 82 and 83. The shank of the bolt 81 extends,v through apertures in the two stri s 62 and 70 as well as through an aperture 3 and the strip 72. Moreover, a washer 78 is posi` tioned between the end of the strip 62 and the end of the strip`70`, for the same purpose strip 62 associated with the bolt 75' from bej as the previously described analogous washer. A terminal member or washer 84 is located between the locknut 82 and the endof the strip 72 and serves to secure one end of the winding 60 to the bolt 81, as shown in Fig. 3. It will be evident that the frame is connected to the contact boltl or post 75 and one end of the winding is connected to the contact bolt or terminal post 81 which post is insulated from the frame by means of the nsulating washer 77. The circuit is completed through the means of the movable contact arm 46.

Furthermore, by referring to Fig. 1 it will be noted that the portion 22 of the frame 2O is provided with a plurality of vents or openings 77 which openings serve as a means of ventilation. These vents permit a continu-- ous change of air to take place on the inside of the frame thereby increasing the heat radiating properties of the entire unit. Then, too, it should be noted that each of thewashers 84 and 78 has formed integral therewith a terminal portion to which an end of an electrical conductor may be fastened. I have designated these terminals by the reference characters 78 and 84.

In Figs. 10 and 11 I have illustrated my invention applied to a potentiometer. The primary difference between this device and that described in connection with Figs. 1 to 9 inclusive, resides in the provision of three terminals or binding posts instead of two. In this form of the invention the posts or bolts 75 and 81 are both insulated from the frame 20 by means of washers such as the insulating washer 71 shown in Fig. 5. The opposite ends of the windings 60 on the strip are secured to these bolts 75 and 81. Located between the binding posts 75 and 81 is an additional terminal 9() which is originally secured to the concave portion 22 of the metallic frame 20 by means of a rivet 91. Thus it will be readily obvious that my invention can be'readily applied to both rheostats and potentiometers. l

Of course, it is to be understood that the present invention isnot to be limited by my specific disclosures but only insofar as defined by claims.

I claim:

1. A resistance strip for current controllers comprising a strip of insulating material having a plurality of convolutions of wire of wire wound thereon transversely of the strip, the convolutions adjacent one end of the strip being distorted and wedged laterally into the side of the strip in order to prevent the wire from unwinding.

3. A resistance strip for current controllers comprising a strip of insulatingmaterial having wire windings thereon, the wire adj acent one end of the strip being distorted and forced into one edge of the strip with its exposed surface flush with the adjacent exposed edge of the insulator strip and said wire adjacent one end of the strip also being pressed laterally into theside of the strip in order to` prevent said wire from unwinding.

4. In an electric current control device, a

frame, contact mechanism associated there-fy with including a contact arm, and a resistance strip associated with said frame and cooperable with said contact arm, said strip including an insulator core having a plurality of turns of wire thereon, the last few turns of said winding'adjacent the off point of said contact arm being distorted and wedged into the strip to increasing depths toward the last turn which is wedged with its exposed surface fiush with the adjacent edge of the insulator strip to provide a smooth takeoff for the arm. f

5. In an electric current control device, a frame, contact mechanism associated therewith including a contact arm, and a resistance strip associated with said frame and cooperable with said contact arm, said strip including an insulator core having a plurality of turns of wire thereon, the winding adjacent the off point of said contact arm being pressed into the strip with its exposed surface fiush with the adjacent edge of the insulator strip to4 provide a smooth takeoff 'for the arm, and said wire adjacent one end also being distorted and wedged laterally into the side of the strip in order to prevent said wire from unwindlng.

In witness whereof, I hereunto subscribe my name this 8th da of October, 1926.

N EVVION SCHELLENGER.

the scope and spirit of the appended v wound thereon, the convolutions adjacent one 

